In recent years, it is known a technology of controlling, for example, a load provided in a consumer or a dispersed power source provided in a consumer by a power management apparatus (for example, HEMS: Home Energy Management System) provided in each consumer.
Examples of the dispersed power source may include a fuel cell unit including a fuel cell such as an SOFC (Solid Oxide Fuel Cell). Examples of the dispersed power source may include a power generation equipment that utilizes clean energy such as sunlight, wind power, or geothermy.
In this case, generally, power supplied from the fuel cell is controlled to follow power consumption of the load provided in the consumer.
Further, a technology of reducing a price selected by a user or CO2 emission by changing a type of power supply that supplies power to each load and operation time of each load, is also proposed (for example, Patent Literature 1).
Meanwhile, when the output of the fuel cell is decreased, the power generation efficiency of the fuel cell is decreased. That is, in a state where the output of the fuel cell is low, the unit price of power generation of the fuel cell is increased. Therefore, it should be considered which is more appropriate to use power supplied from a grid and the power supplied from the fuel cell, or power generated by another power generation equipment. In other words, there is a case where advantage cannot be gained in terms of price by only following the power consumption of the load and controlling the fuel cell.